1. Field of the Invention
The present invention relates to a temperature sensitive indicator for irreversibly indicating whether the temperature is at least or no more than a predetermined temperature, and particularly to a temperature sensitive indicator capable of visually confirming whether exposure to an environment of at least or no more than the predetermined temperature has occurred.
2. Description of the Related Art
In recent years, temperature control has been important in quality control of commercial goods and products. For example, when fresh products, such as fresh food and cut flowers, medical goods, and semiconductor materials are exposed to a predetermined temperature or higher without being provided with temperature control, the qualities of these commercial goods and products might be lowered or degraded and bacteria might grow, causing rottenness.
For this reason, strict temperature control is necessary not only at the time of production of these commercial goods and products but also at the time of deliver and storage of the same, and a temperature sensitive indicator is used as the means for continuously monitoring the temperature control.
The one described in Patent Document 1 (Japanese Patent Publication No. S58-10709) is proposed as such a temperature sensitive indicator. The temperature sensitive indicator described in this Patent Document 1 is described with reference to FIGS. 3 and 4.
This temperature sensitive indicator 100 has a channel-shaped carrier 102, and this channel-shaped carrier 102 has a base 104 and side walls 106 extending upward from the rims on both sides of the base. Each of the side walls 106 is in a waveform and has an upper groove 108, a central part 110, and a lower groove 112. The channel-shaped carrier 102 is made of a flexible hard material that is appropriate for spreading the both side walls 106 outward by force of hands.
Consequently, a permeable material 114 is placed on the base 104. The permeable material 114 is formed from blotting paper so as be provided with a straight or bent path and a display area 116.
A porous matrix 118 that absorbs a fluid saturant is attached to a matrix holder 120. As the fluid saturant absorbed by the porous matrix 118, for example, a substance that is solid at a temperature for storing frozen food but becomes liquid at a temperature for defrosting food (room temperature, for example) is selected.
Furthermore, the matrix holder 120 has an upper protective cover part 122 and a thick end part 124 with a slot 126. The porous matrix 118 is inserted into the slot and held on a lower surface of the cover part 122. Note that this display device 100 further has attachment means 128 configured by a pressure sensitive adhesive layer 130 and a removable protective liner 132.
In order to operate this temperature sensitive indicator 100, the upper protective cover 122 and the channel-shaped carrier 102 are pressed together. Consequently, the cover 122 bends the side walls 106 outward and moves toward the permeable material 114, and then the permeable material 114 comes into contact with the porous matrix 118.
The porous matrix 118 and the upper protective cover 122 overlapped thereon are deflected toward the permeable material 114 by the elasticity of the side walls 106 within the lower groove 112. In this manner, the porous matrix 118 and the permeable material 114 are held tightly in a contact state by the elasticity of the side walls 106.
Because the porous matrix 118 and the permeable material 114 are adhered tightly to each other fluid flows out of the porous matrix 118 into the permeable material 114 when the temperature becomes a predetermined temperature or higher, and the fluid moves inside the permeable material 114. Generally, the fluid is visibly colored with a dye that is included in the fluid, and therefore it is possible to visually confirm and determine that a commercial good or product with the temperature sensitive indicator 100 is exposed to an environment of at least or no more than the predetermined temperature. Further, because the permeable material 114 has the straight or bent path and the display area 116, the forward travel of the fluid can be observed, and the time at which the commercial good or product is exposed to the environment of at least or no more than the predetermined temperature can also be determined.
Patent Document 1: Japanese Patent Publication No. S58-10709
Incidentally, in the temperature sensitive indicator disclosed in Patent Document 1, because the fluid saturant is absorbed by the porous matrix, the fluid saturant changes to a liquid phase and evaporates when storing the temperature sensitive indicator in a high-temperature environment, and there is a possibility that the liquid solution of the chemical substance evaporates even when the fluid saturant does not change to a liquid phase. For this reason, a problem in storing the temperature sensitive indicator is that the temperature of the temperature sensitive indicator itself needs to be controlled.
Moreover, in order to operate the temperature sensitive indicator, the upper protective cover and the channel-shaped carrier are pressed together. Therefore, a problem in pressing the upper protective cover and the channel-shaped carrier together is that the fluid saturant detects the temperature of a finger through the upper protective cover.
The present invention was contrived to solve the problems described above, and an object of the present invention is to provide a temperature sensitive indicator that is capable of easily control the temperature of the temperature sensitive indicator itself and is not affected by the temperature of a finger when the temperature sensitive indicator is operated.